WASHINGTON (AP) — The Obama administration estimates that 100 to 150 people have died from chemical weapons attacks in Syria.

The White House blames the Syrian government for the attacks and says the casualty data is likely incomplete. It says it has no reliable, corroborated information to suggest that the Syrian opposition in the country’s civil war has acquired chemical weapons.

The White House, in a statement issued late Thursday, says the use of chemical weapons “violates international norms and crosses clear red lines.”